"All of these things are coming together ... to give cloud storage providers a black eye. Anyone who was on the fence about cloud storage may be off of it by now," said Gartner research analyst Adam Couture.

More importantly, the closures and outages leave users with an important question: What happens to their data when the cloud they use evaporates?

Currently, there's no way for a cloud storage service provider to directly migrate customer data to another provider. If a service goes down, the hosting company must return the data to its customer, who then must find another provider or revert back to storing it locally, according to Arun Taneja, principal analyst at The Taneja Group.

SNIA and migration

The Storage Networking Industry Association's Technical Work Group is developing an API called the Cloud Data Management Interface that would allow providers to migrate customer data from one vendor's cloud to the next -- a move aimed at alleviating vendor lock-in.

That API, if adopted by the industry, will become more important over the next several years as nearly three out of four cloud storage companies that cropped up in recent years whither and die, according to Taneja.

"There's no way for Amazon to send your data directly to another storage service provider like Nirvanix. The transfer has to happen back to the customer," Taneja said.

Taneja added that as long as the cloud service provider is still online, if a user gives Nirvanix permission, it can access another cloud provider's service using the customer's log in information in order to download their data as a type of "cloud-to-cloud" migration.

But, he added, "there are no rules or regulations about [cloud storage] data deletion today."

Even if you ask a cloud vendor to delete your data, it's not necessary gone -- at least, not right away. Cloud service providers use a "garbage collection" method for deleting old data. First, data is marked for deletion. Then the actual erasure or overwrite process takes place at a later date, sometimes months later, Taneja said.

That can be of particular concern in highly regulated industries such as financial services or for legal entities such as law firms.

Storage service providers dropping

Over the past year, storage service providers have been dropping quickly.

EMC last year announced it was shutting down its Atmos Online storage service because it was competing with its own resellers. At the time, EMC offered no guarantee that its customers could retrieve their data once the service closed. On the heels of the Atmos shutdown, cloud storage provider Vaultscape also closed.